Process of obtaining photographic images



?etented' duly 3% l9 2,353,661 success or on'rsmmo enoroensrmo muons BlaGaspfir, Hollywood, Calif asslgnor to Chromozen, Incorporated, acorporation of Nevada No Drawini', Application December 1, 1940,

Serial No 369,123

5 Claims.

My invention relates to the production of photographic images and, moreparticularly, to the production of photographic reversal images.

It is common practice to produce photographic reversal images from asuitable emulsion of lightsensitive silver bromide by exposing a portionof it to produce a latent image therein, developing this image, andthen, without firing the image, removing the developed x'netallic silverdeposit by an oxidizing agent without removing the unexposed silverbromide. The remaining silver bromide is then blackened by exposing itand developing it, or it may be converted by a chemical agent, such forexample as sodium hydrosulphite.

In the known processes for the production of reversal images, the silverimage first produced is removed either by a solution of sulphuric acidand potassium bichromate or a solution of sulphurie acid and potassiumpermanganate. Both of these solutions strongly aflect the gelatin, or inthe case of a paper support, the paper fiber;

- furthermore, they affect other substances such as sensitive and easilydestroyable substances for colcrine that may be contained intheemulsion. More particularly, they may aiiect dyes serving as filterdyes, sensitizing dyes or dyes serving later on in the process for theproduction of dye im-' ages. Likewise, in the case where a dye formingsubstance is used in the'emulsion, they may affect the dye formingsubstance.

it is, therefore, an object of my invention to provide on improvedmethod of treatment oithe initial silver image contained in aphotographic syer in a reversal process whereby the same may be bleachedand removed without the use or strong acidic reactions or energeticoxidizing spouts;

Another object of my invention is to provide on improved method offorming reversal images in photographic layers containing a developedsilver image in a light-sensitive emulsion and a uniformly distributedsubstance for coloring which is sensitive to and is destroyed by knownbleaching baths having acidic properties.

Another object of my invention is to provide such a method wherein theinitiel silver image in a reversal process is transformed into a silversalt and afterwards dissolved in a bath by the formation off a complex.

Another object oi my invention is to provide such a method'oi formingreversal imageswhere-= in'the initial silver image of a layer is treatedto form 2. silver salt and the silver salt is later -dis= solved by theformation or a complex without deferricyanide and sodium chloride.

straying or deleteriously affecting the coloring substance employed inthe layer.

A further object of my invention is the pro-. vision of such a method inwhich the dissolution of the silver salt under complex formation doesnot result in the dissolution of the remaining silver bromide.

These and other objects of my invention will appear as the descriptionproceeds, and its scope will be pointed out in the claims appendedhereto.

My invention will be best understood by an illustration of itsapplication to an emulsion suitably adapted for the production ofphotographic reversal images.

, Example 1 After the initial image has been produced in the emulsion bysuitable exposure of 'a lightsensitive silver bromide gelatin emulsionand the latent image has been developed, but before the image has beenfixed, the emulsion is treated with a mild oxidizing agent, such, forexample, as a 540% solution of cupric chloride, which acts to .iorm thedeveloped silver image into silver chloride. The emulsion is thenwashed, and the silver chloride is dissolved by a medium which does notdissolve silver bromide. For this purpose a saturated solution of sodiumchloride is used, and it has been found that this treatment results inthe dissolution of the silver chloride in 5 to 20 minutes, dependingupon the strength of the image. Alter the silver chloride has beendissolved out, the remaining silver bromide is developed in the usualmanner to form the reversal silver imae'e.

Instead oi using cupric chloride as an oxidizing agent, I might use a2-57,) solution of potassium 'ferricyanide containing 2-5% of sodiumchloride for the purpose of converting the silver image to a silversalt. In this specification the term mild oxidizing agent" characterizesa solution such as copper chloride or a dilute solution or potassiumSuch SOhl'. tions are indiflerent to the extent that they do not afiectthe gelatin emulsion, or the support, or destroy dyes or dyeformingsubstances formhis part of a photographic material which is treated inthe solutions. In addition, they-are indifierent in that they do notsheet the sensitivity of the undeveloped silver'bromideto as great anextent as the conventional. acidic potassium permanganate or bi-chrnmatesolutions previously used as bleaches in the reversal process.

By the use oi the above cupric chloride bleach and treatment with aconcentrated solution or reactions and energetic oxidizing agents.

My invention is not limited to'the use of a concentrated sodium chloridesolution for the purpose of removing the silver chloride resulting frombleaching the initialsilver image. Any other completely neutral solutionof a substance can be used which dissolves the silver chloride undercomplex formation and leaves the unexposedsilver bromide undissolved. Inthe same manner, instead of using a solution of cupric chloride orpotassium ferricyanide and sodium chloride for" the purpose ofconverting the silver image into a silver chloride image, any other mildoxidizing agent could beused which operates to convert 'the silver intoa silver salt which is dissolved.

more readily under complex formation than silver bromide. For example,th developed silver might be transformed into silver rhodanide inthewell known manner.

All of these solutions have the common property that they'do not affectthe gelatin. Likewise,- -if the emulsion is coated on a paper support,they do notaifect the paper fiber. Furthermore, the practice of theprocess comprised in my invention has the added advantage that'thesensitivity of the silver bromide is-influenced to a smaller extent thanit would be in the case of treatment with bichromate or permanganate. Itis, therefore, especially suitable in those photographic processes wherethe emulsion is again exposed prior to the second development.

My invention is equally applicable to a single layer, or to multilayermaterials such a multilayer multicolor photographic material. More whichtransforms the silver image in each of the layers into silver chloride.After washing. the material is treated in a saturated solution of sodiumchloride for 10 to 20 minutes. During the treatment the silver chlorideis dissolved by the formation of a complex. By this treatment the silverimages in each of the layers are removed -ment a multi-color image isobtained. The remaining silver may be removed by treating the materialas previously set forth or it can be removed in accordance with theprocess described in my United States Patent No. 2,042,253 dated May 26,1938.

- Example III A silver bromide layer containing uniformly distributedtherein 1 g. per square meter of the particularly, it is applicable toemulsions containing coloring substances distributed uniformly thereinwhich coloring substances are defined for ed claims as dyes..ordye-forming substances such asthose used for color development or forthe color-forming substances, the full advantages of my improved methodare realized in that the silver image can be converted into a reversalim-' age without affecting these dyes or color-forming substances as isdisclosed in the following examples: 7

Example II On a paper support is placed a red sensitized I silverbromide emulsion containing 0.3 g. per

square meter of Diamine Pure Blue F.

' the purposes of this specification and the appendsulfate ester salt ofthe leuco-compound of (A) hexa-brom-indigo or (B)6.6"di-brom-dimethylbis-thionaphthene indigo is coated on a reflectingor transparent support. The material is exposed by printing through anegative or by direct exposure in a camera. The material is then treatedin accordance with Example I except that after the second developmentthe dye image-is formed by the methods disclosed in my United StatesReissue Patent No. 21,513 granted July 23, 1940. More particularly, Iprefer to transform the silver image into a dye image by the use of afresh solution consisting of 1/10% potassium bichromate and 1% ofhydrobromic acid. After 5'to 10 minutes treatment a reversal blue dyeimage is formed in the layer if the material contains the compounddesignated by (A) and a reversal magenta dye' image will be formed inthe layer if it contains the compoimd designated by (B). After thistreatment th silver and also the unusedleucocom'poundisranovedinanalkalinetreat--ingbathpreferablyonecontainingasmallquan- (Schultz-seventh edition,170.511) distributed uniformly therein and a green sensitizedsilverbromide emulsion is placed on top thereof containing 0.4 g. persquare meter of Sirius-Rubin B (Ullmann-Enzyklop'idie der TechnischenChemie, vol. 9, page 524).

' posed through color separation negatives and the silver imagesdeveloped in each of the layers. The multi-layer material is thentreated in a bleaching bath consisting of a 5 to 10% soiution of Anuppermost layer -of silver bromide emulsion containing 0.5 g. per

cupric chloride for a period of 5 toll) minutes" tity of acetone ormethyl alcohol. The reversal treatment preceding the transformation ofthe silverimagetothedye imagedoesnot oxidizethe leuoo compoundstothedyeaswouldresultifthe known acid bichromate andrpermanganate silver bleachsolutions were employed.

.Emnrple IV I 'Example 1. The second development is carried on with thefollowing color-forming developing solution:

Diethyl pars-phenylen dlamine -g 1 Sodiumcarbonate (anhydrous g 20Sodiumsulflte g .0 water or 1,000

By this treatment a reversed magenta dye image and asilver imageisformedrAfter washing, the

silver-imueis removed y treating't c tain methods embraced therein forthe purpose of explaining its principle and its application, but it willbe obvious to those skilled in the art that many modifications andvariations are possible. I aim, therefore, to cover all suchmodifications and variation as fall within the scope of my inventionwhich is defined in the appended claims.

What I claim is:

l. A method of producing a reversal dye image in a light-sensitivesilver halide emulsion containing a developed silver'image and an easilydestroyable coloring substance distributed uniformly therein, whichcomprises the steps of treating said emulsion with a mild oxidizingagent which convert said developed image to a/ silver salt image otherthan the silver halide comprising said light sensitive emulsion withoutdestroying the uniformly distributed coloring substance and complexwithout ailecting the undeveloped silver bromide or destroying thecoloring substance.

3. A method of producing a reversal dye image in a light-sensitivesilver bromide emulsion containing a developed silver image and aneasily destroyable coloring substance distributed uniformly therein,which comprises the steps of treating said emulsion with a solution ofcupric chlosubsequently treating the silver salt image with I ,stroyingthe uniformly distributed coloring substance and subsequently treatingthe silver salt image with a completely neutral solution comprisin: asaturated solution of sodium chloride to ride to produce a silverchloride image without destroying the uniformly distributed coloringsubstance and subsequently treating the silver chloride image with acompletely neutral solution comprising a saturated solution of sodiumchloride to dissolve the silver chloride image by formation of a complexwithout affecting the undeveloped silver bromide or destroying thecoloring substance.

4. A method of producing a reversal dye image in a light-sensitivesilverbromide emulsion containing. a developed silver image and aneasily destroyabie coloring substance distributed uniformly therein,which comprises the steps of treating aid emulsion with a solution ofpotassium. ferricyanide and sodium chloride to bleach said image byforming a silver chloride. image without destroying the uniformlydistributed coloring substance and subsequently treating the silverchloride image with a completely neutral concentrated solution of alkalichloride to dissolve the silver chloride image by formation of a complexwithout affecting the undeveloped silver bromide or destroying thecoloring substance.

5. A method Of producing a reversal dye image in a light-sensitivesilver'bromide emulsion condissolve the silver salt image by formationof a taining a developed silver image and an-easlly destroyable coloringsubstance distributed uniformly therein, which comprises the steps oftreating said emulsion with a solution of'potasslum ferricyanide andsodium chloride to bleach said "imag by forming a silver chloride imagewithoutdestroying the uniformly distributed coloring substance andsubsequently treating the silver chloride image with a completelyneutral salt solution comprising a concentrated solution of sodiumchloride to dissolve the silver salt image by formation of a complexwithout affecting the undeveloped silver bromide or destroying thecoloring substance.

ism-A GAsPAR.

